Lithium secondary battery separator having enhanced adhesive strength to electrode and improved resistance characteristics, and lithium secondary battery comprising lithium secondary battery separator

Patent metadata

Field	Value
Publication number	US-12255352-B2
Application number	US-202017632186-A
Country	US
Kind code	B2
Filing date	Oct 29, 2020
Priority date	Oct 29, 2019
Publication date	Mar 18, 2025
Grant date	Mar 18, 2025

Abstract

A lithium secondary battery separator with excellent adhesive strength and air permeability is disclosed. The lithium secondary battery separator includes a porous polymer substrate; and a porous coating layer containing inorganic particles and a binder. When the binder is present as a binder specimen with a thickness of 0.4 mm after pressurization at 190° C., the binder specimen comprises a first binder having a tan δ peak at 15° C. to 27.6° C. and a second binder having a tan δ peak at 8° C. to 20.2° C., as measured by dynamic mechanical analysis (DMA).

First claim

What is claimed is:

1. A separator for a lithium secondary battery comprising:
a porous polymer substrate; and
a porous coating layer on at least one surface of the porous polymer substrate,
wherein the porous coating layer comprises a binder and inorganic particles wherein each inorganic particles has a binding state,
wherein the binder bonds the inorganic particles to one another, wherein the inorganic particles retain their binding states, and wherein the binder bonds the inorganic particles to the porous polymer substrate and the inorganic particles retain their binding states,
the inorganic particles form interstitial volumes, wherein the inorganic particles are in contact with one another, and the interstitial volumes among the inorganic particles become vacant spaces to form pores of the porous coating layer,
the binder comprises a first binder and a second binder, the first binder having a tan δ peak at 15° C. to 27.6° C. and the second binder having a tan δ peak at 8° C. to 20.2° C., as determined by dynamic mechanical analysis (DMA) of a specimen of the first binder and a specimen of the second binder each having a thickness of 0.4 mm after pressurization at 190° C., and
the first binder is present in an amount of 5 wt % to 20 wt % and the second binder is present in an amount of 80 wt % to 95 wt %, based on 100 wt % of a combined weight of the first binder and the second binder.

2. The separator for the lithium secondary battery according to claim 1 , wherein the binder further comprises a third binder, the third binder having a tan δ peak at −12° C. to 0° C., as determined by dynamic mechanical analysis (DMA) of a specimen of the third binder having a thickness of 0.4 mm after pressurization at 190° C.

3. The separator for the lithium secondary battery according to claim 2 , wherein the third binder is present in an amount of 8 wt % to 25 wt % based on 100 wt % of a total weight of the first binder, the second binder and the third binder.

4. The separator for the lithium secondary battery according to claim 3 , wherein the third binder comprises poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE).

5. The separator for the lithium secondary battery according to claim 1 , the specimen of the first binder has a behavior at a phase angle of less than 45°, as determined by an advanced rheometric expansion system (ARES) at 190° C.

6. The separator for the lithium secondary battery according to claim 1 , wherein the specimen of the second binder has a behavior at a phase angle of 45° or more, as determined by an advanced rheometric expansion system (ARES) at 190° C.

7. The separator for the lithium secondary battery according to claim 1 , wherein the first binder is present in an amount of 5 wt % to 15 wt % and the second binder is present in an amount of 85 wt % to 95 wt %, based on 100 wt % of the combined weight of the first binder and the second binder.

8. The separator for the lithium secondary battery according to claim 1 , wherein the first binder satisfying the tan δ peak condition is at least one of poly(vinylidene fluoride-tetrafluoroethylene) (PVDF-TFE), poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE), or PVDF-HFP-acrylic acid graft copolymer (PVDF-HFP-AA).

9. The separator for the lithium secondary battery according to claim 1 , wherein the second binder satisfying the tan δ peak condition is poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP).

10. The separator for the lithium secondary battery according to claim 1 , wherein the porous coating layer further comprises a dispersing agent.

11. A lithium secondary battery, comprising:
a positive electrode,
a negative electrode, and
a separator interposed between the positive electrode and the negative electrode,
wherein the separator is the separator for a lithium secondary battery as defined in claim 1 .

Assignees

• Lg Energy Solution Ltd

Inventors

• Kim Bong-Tae
• Lee Joo-Sung
• Jung Kil-An

Classifications

• H01M50/431

  Inorganic material · CPC title

• H01M50/491

  Porosity · CPC title

• H01M50/426

  Fluorocarbon polymers · CPC title

• Y02E60/10

  Energy storage using batteries · CPC title

• H01M50/443

  Particulate material · CPC title